1. Field of the Invention
The present invention relates to a method for manufacturing a sintered compact, a sintered compact manufactured by the method and a cell culture base formed from the sintered compact.
2. Description of the Prior Art
Hydroxyapatite, which is a kind of calcium phosphate based ceramics, is the main component of bone and teeth, and therefore it has excellent biocompatibility. Such hydroxyapatite is used as biomaterial for artificial bone, dental implants, medical or dental cement, and the like. Further, since hydroxyapatite has high affinity with cells, proteins or the like, it is also used as a material for a carrier for cell culture, or a material for use in separation of proteins, or the like. For example, Japanese Patent Laid-open No. 2003-047461 discloses an apatite sheet which is to be used as a carrier for cell culture.
In a case where hydroxyapatite is used as biomaterial for artificial bone or dental implants or the like, sintered compacts of hydroxyapatite are practically used. In this case, the sintered compact is required to have sufficiently high mechanical strength. In order for the sintered compact to meet such requirement, it is necessary for the sintered compact to have high relative density. That is, there is a need to manufacture a high-density sintered compact.
Further, since the occurrence of cracking or the like inside the sintered compact leads to lowering of mechanical strength, inspection of inside of the sintered compact (inspection for determining whether or not cracking or the like exists) is made after manufacturing. For this reason, it is preferred that the sintered compact has transparency.
The transparency of the sintered compact tends to increase with increase in density. From such a viewpoint, it is important to manufacture a high-density sintered compact.
Conventionally, such a sintered compact has been manufactured by molding hydroxyapatite powder into a desired shape to obtain a green compact and then sintering the green compact.
However, it is difficult to obtain a sintered compact having satisfactorily high relative density (that is, high-density sintered compact) by such a conventional manufacturing method.
Further, in the apatite sheet disclosed in Japanese Patent Laid-open No. 2003-047461 mentioned above, the condition of cells adhering to the apatite sheet is observed using a SEM. In the case where cells are observed with a SEM or the like, the cells will, of course, die. On the other hand, in the case where cells are observed with an optical microscope, it is possible to observe living cells, but it is difficult to observe an interface between the cells and the apatite sheet. This is because the apatite sheet has no light permeability so that it is difficult to optically observe the cells.
For this reason, there are demands for apatite sheets having high light permeability.
Furthermore, in recent years, in various kinds of cell culture, there is a case where an instrument having surfaces to be contacted with cells which are coated with a calcium phosphate based material is used. By using such an instrument, cells can be cultured under conditions similar to those in a living body (see Japanese Patent No. 2657403, for example).
Further, since the calcium phosphate based material is a main component of bone, it is also possible to make an evaluation of affinity of various kinds of cells with bone by using such an instrument.
Such an instrument is made by coating a metallic, plastic, or glass substrate with a calcium phosphate based material. However, it is hard to say that the substrate is completely coated with a calcium phosphate based material, so that there is a possibility that a part of the substrate is exposed. Therefore, in a case where such an instrument of which substrate is partially exposed is used, there is a possibility that affinity of cells with glass or the like is evaluated instead of affinity of cells with a calcium phosphate based material (that is, bone).
Further, it is desired that an instrument itself with cultured cells can be transplanted into a living body after the completion of cell culture. However, a problem exists in that since such an instrument is mainly made from glass or the like, the instrument itself can not be transplanted into a living body as it is.